Art of controlling furnace-gases.



No. 789.844. PATENTBD MAYQl, 1905. J. W. DOUGHERTY. ART 0F GQNTROLLINGFURNACE GASES.

APPLIUATION FIL-ED AUGx 30, 1904.

NiTED STATES Patented May 16, 1905.

vPATENT OFFICE.

ART OF CONTROLLING FURNACE-GASES.

SPECIFICATION forming part of Letters Patent No. 789,844, dated May 16,1905.

Application mea August so, 1904. serial No. 222,762. i

` at Steelton, in the county of Dauphin and State of Pennsylvania, haveinvented certain new and useful Improvements in the Art of ControllingFurnace-Gases; and I do hereby declare the following to be afull, clear,and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same,reference being had to the accompanying drawings, and to letters ofreference marked thereon, which form a part of this specification.

My invention relates to the art of starting or Lblowing in ofblast-furnaces for smelting of iron ores by controlling the furnacegasesto avoid explosions commonly attending the blowing in of such furnaces.

The object of this invention is to provide a means by which a modernblast-furnace may be started or blown in without dang'er of explosionsand by immediate application of blast made to produce marketable metal,avoiding the dangers and the explosive results of the common methods.

At present the universal custom of blowing in blast-furnaces is tocharge the furnace first with a large quantity of wood, then a largequantity of coke, then a quantity of coke with limestone, and thencharges of ore, coke, and limestone in proper proportions, after whichthe wood is ignited and the charge allowed to burn for about twenty-fourhours by natural draft, the products of combustion passing off throughthe hopper around the bell, left open for that purpose. While undernatural draft with cold air combustion is imperfect and the furnacekeeps comparatively cool and is liable for some time after blast isapplied to work cold, producing iron which is not marketable and mustafterward be resmelted at much cost of labor, fuel, and metallic loss.In the largest furnaces the quantity of such unmarketable metal producedwhile getting the furnace started is sometimes upward of one thousandtons.

The reason for not putting the blast on at once is the danger ofexplosion of the explosive mixture of the resultant gases and the air inthe furnace-top, pipes, 85e., for conducting the gases to the boiler andthe hot-blast stoves Where the gases are burned and utilized. Much timehas to be allowed for the gases to displace the air contained in saidpipes, &c., before it becomes safe and practicable to permit ignition ofthe gases under the boiler or in the hot-blast stoves without causingexplosions liable to effect destruction of costly structures and wreckthe furnace. It has frequently happened that after experienced furnacemen have judged it to be safe to commence ignition and consumption ofgas there still remained in the pipes, Ste., sucient air to form anexplosive mixture of air and gas, which upon ignition exploded withgreat violence, causing great destruction.

Referring to the drawing, in which like parts are similarly designated,I have illustrated in section a double-bell furnace and thedust-collector of well-known type.

The blast-furnace proper is designated at a and is of the usualconstruction with a double bell 7) Z1' at the top and the down-comer cfor carrying the `furnace-gases to the dust-collector c', from whichthese gases are distributed through pipes, as d, to the places ofconsumption.

In some structures there is a valve e controlling the gas to the pipe orpipes CZ; but in 'many there are no valves at this point, the

only valves being at the device where the gas is to be consumed-boilers,hot-blast stoves, and the like.

After the furnace has been charged with proper starting materials allvalves are closed, also any doors that may be in the pipe or pipesbetween the dust-collector and boilers or hotblast stoves. The bell, ifit is a single-bell furnace, or both bells, if it is a double-bell.furnace that is to be blown in, are left open. I then inject steam intothe dust-collector c' by a pipe f, controlled by avalve Steam from theboilers is admitted until there is seen agood iow of white vapor fromthe top of the furnace due to the ascending steam. The bell or bells arethen closed and the bleeder or bleeders c' are opened, first one of themuntil vapor is seen to rise from it, which is then closed, and then theother bleeder is similarly opened and closed, if there happens to be twobleeders on the furnace. I now open valve e, or, if there is novalve atthis point, open a valve at a point where the gas is to be burned,either at the boilers or stoves. The steam will now begin to work downto the opening thus made; but as soon as this opening has been made thefurnace is lighted at the bottom, and after lighting it the hot-blast isturned on and in a few minutes steam will be found issuing from theopening made at the stoves or boilers. As soon as gas comes along ingood quantities the steam is turned off and the gas is admitted to thestoves and boilers and burned. It will thus be seen that I drive out theair from the top of the furnace and its pipe connections as much aspossible with steam, and thus cause a cushion of steam to be propelledin front of the furnace-gases, efectually driving out any residual airin front of it and avoiding the formation of a'n explosive mixture.

In the foregoing description of the method of using my improvement itshould be understood that where I mention hot blast it is on theassumption that the furnace I am about to blow in is near anotherfurnace already in operation, as is usual in large works, where theplant usually embraces several furnaces, in which case blast that isheated in hot-blast stoves in regular operation may be conducted to thefurnace blowing in.

When applied to an isolated furnace or where hot blast cannot be haduntil the stoves of said furnace become heated upgsay with gas producedby said furnace-it is obvious that the blast which I will applyimmediately after lighting the furnace will necessarily be cold, inwhich case more time will be required to bring the furnace to goodcondition than if hot blast were immediately available; but neverthelessfreedom from danger of explosions will be secured and the time requisitefor obtaining good marketableiron will be greatly shortened by the useof my improvement.

I may also inject steam at one or more places; say also at the top ofthe down-comer, as shown at la.

In a hundred-foot furnace recently blown in by me the above procedurewas used, the gas being first admitted to the Kennedy burners at thestoves, while from the top of the furnace to the place where'the gas waslighted is about tive hundred feet. Steam was admitted to thedust-collector through a two-inch pipe under a pressure of eightypounds. The furnace produced iron twenty-four hours earlier than by theold method of blowing in and at the same time produced marketable ironfrom the start with not the semblance of the least explosion when thegas was turned on. In case the down-comer and dust-collector arecompletely cold it is well to give-them a preliminary heating, mostconveniently done' by building a iire in the dust-collector and allowingthe smoke to ascend the down-comer and pass out of the top of thefurnace. This will heat the pipes and prevent too great a condensationand consumption of the steam.

After a stop in blowing it is also advisable to inject steam' in thepipes before the blast is again put on and the gas again lighted, so aslto avoid explosion. 4

After the blast has beenturned on it may be desirable to light the gasat the top of the furnace, at the same time turning on the steam, andwhen a good flow of steam is obtained close the top of the furnace andsend the mixture of gas and steam to the points of use-boilers orstoves. The steam will decrease the temperature of the gases to belowtheir critical temperature as well as act as a diluent to preventexplosions. It will also assist the blast to blow the gas through thedown comer and other connections to the points of use.

Having thus described my invention, what I claim as new therein, anddesire to secure by Letters Patent, is-

1. The art of controlling furnace-gases, which consists in placing infront of the gases emanating from the furnace a body of an inert gas orvapor in sufficient quantity to pre. vent explosion, substantially asdescribed.

2. The art of controlling furnace-gases, which consists in placing infront of the gases emanating from the furnace a body of steam insufficient quantity to prevent explosion, substantially as described.

3. The art of starting or blowing in blastfurnaces, which consists indriving the air IOO from the furnace and its gas-pipe connections bymeans of steam, then starting the furnace and applying forced' blast togenerate gas and drive the steam and any remaining air in front of saidgases, substantially as described.

4. The art of blowing in blast-furnaces, which consists in placing abody of steam in the top of the furnace and in the pipes between thefurnace and place of use of the gases, and then turning on the blast,and driv- I IO ing the steam and air in front of the gases by reason ofthe energy of the blast, thereby avoiding explosion,substantially asdescribed.

5. The art of blowing in blast-furnaces, which consists in forcing airout of the gas- II5 pipes and connections by means of steam and thenturning on the blast to force a body of steam in front of thefurnace-gases to the point of their consumption, substantially asdescribed.

6. The art of blowing in blast-furnaces, which consists in rst heatingthe gas-conveying pipes leading from the furnace, then driving out theair therein by steam and then turning on the blast, whereby a body ofsteam T25 will be driven through said pipes in advance of the gases,substantially as described.

7 The art of blowing in blast-furnaces, which consists in temporarilyinjecting into the furnace-gases emanating from the furnace 130 proper abody of steam sullcient to prevent the formation of an explosive mixtureand using the gases at a suitable point of consumption after theconnections with the furnace have been cleared of air by said body ofsteam, substantially as described. Y

8. The art ofcontrolling the gases of metallurgical furnaces usingblast, Which consists in temporarily injecting a body of inert gas orvapor in front of the furnace-gases in sufiicient quantity to preventexplosion and in a direction opposite to the natural flow of said gases,and then applying blast to the furnace, substantially as described.

9. TheA art of blowing in blast-furnaces, which consists in filling thetop of the furnace, the gas-pipes and their connections With steam,lighting the furnace, throwing on the blast and venting the steam fromthe furnace and pipes at the points of consumption of the gases fromsaid furnace, substantially as described.

In testimony that I claim the foregoing as my invention I have signed myname in presence of two subscribing Witnesses.

JOHN WEBSTER DOUGHERTY.

Witnesses: y

W. H. NELL, Ross M. FREY.

